1. Field
Exemplary embodiments disclosed herein generally relate to a device and a method for displaying an image, a device and a method for supplying power, and a method for adjusting brightness of contents, and more particularly, to a device and a method for displaying an image, by which driving power supplied to an organic light-emitting diode (OLED) panel is feed-forward-controlled based on an image signal supplied to the OLED panel, a heat emission caused by a voltage difference is reduced during driving of red (R), green (G), and blue (B) light-emitting devices by using a power supply voltage VDD, R, G, and B values of image frame data are respectively checked to calculate a maximum current value, a direct current (DC) voltage is converted into a DC voltage having a voltage level corresponding to the maximum current value, power having different amplitudes is supplied according to colors of OLEDs of pixels or a plurality of pixel groups, and a plurality of contents are provided on a screen, a device and a method for supplying power, and a method for adjusting brightness of contents.
2. Description of the Related Art
An image display device processes and displays digital or analog image signals received from an external source and various types of image signals stored in various types of compression formats in an internal storage device.
Organic light-emitting display devices have been actively developed. Such an organic light-emitting display device is a kind of flat panel display and uses an organic light-emitting diode (OLED). In particular, the OLED refers to a self-emission type of organic material which self-emits light by using an electroluminescent phenomenon in which a current flows in an organic compound to emit light. The organic light-emitting display device is driven at a low voltage, is formed as thin film type, and has a wide viewing angle and a fast response speed. Therefore, the organic light-emitting display device does not change an image quality even on a side, and does not leave an afterimage differently from a general liquid crystal display (LCD). If the organic light-emitting display device has a small-sized screen, the organic light-emitting display device has an advantageous competitive price due to a higher image quality and a simpler manufacturing process than the general LCD.
Although not shown in the drawings, the organic light-emitting display device has a structure in which R, G, and B OLEDs are arranged between a single power supply voltage VDD supplied from a power supply terminal and a ground voltage Vss of a power ground terminal, and switch elements such as field effect transistors (FETs) are connected between the R, G, and B OLEDs and the power supply voltage VDD.
In particular, the R, G, and B OLEDs have different driving voltages which vary based on their respective colors, and thus different voltages of both ends are applied to the switching elements respectively connected to the R, G, and B OLEDs according to colors. For example, if a single power supply voltage is 6V, and the R and G OLEDs are respectively driven at voltages of 3V and 4V, a voltage obtained by subtracting 3V from power supply voltage 6V is applied to both ends of the switching element connected to the R OLED. In addition, a voltage obtained by subtracting 4V from a power supply voltage is applied to both ends of the switching element connected to the G OLED.
However, in the organic light-emitting display device, brightness of an image may vary based on a level of a driving voltage. Therefore, a driving voltage supplied to OLEDs in a transition section greatly drops due to a pulse form zone current OLED load characteristic, and brightness of an image may be distorted when the driving voltage greatly drops.
Further, a voltage applied to the switching elements is also referred to as a headroom voltage. Heat is generated due to a difference of the headroom voltage, and thus efficiency of a whole system is deteriorated.
For example, a fixed power supply voltage ELVDD of 12V is supplied as first power ELVDD, which is supplied to a plurality of pixels of the organic light-emitting display device. However, if the fixed power supply voltage ELVDD of 12V is supplied in a situation that R, G, and B values are low gradations (i.e., if a current applied to the OLEDs is a low current), the headroom voltage applied to the switching elements does not reflect R, G, and B gradation levels. Therefore, a large amount of power is consumed in the switching elements due to heat.
In addition, the organic light-emitting display device has a 3-step power conversion structure in order to supply the first power ELVDD which is supplied to the plurality of pixels. In particular, a voltage supply unit has a 3-step power conversion structure including a power factor correction (PFC), a 24V DC/DC converter, and a 12V DC/DC converter which are connected to one another in series. Therefore, first power ELVDD of 12V is supplied to a panel unit of the organic light-emitting display device.
However, in this example, the PFC has power efficiency of about 95%, the 24V DC/DC converter has power efficiency of about 92%, the 12V DC/DC converter has power efficiency of about 94%, and the panel unit has power efficiency of about 80%. Therefore, the organic light-emitting display device has total power efficiency of about 65.7%. Hence, the 3-step power conversion structure causes a large amount of power loss. Further, since the organic light-emitting display device has the 3-step power conversion structure, small-sizing of circuits is limited.
Image display devices have provided various types of contents to satisfy demands of users. Therefore, there have been developed image display devices which simultaneously provide a plurality of contents to allow a plurality of users to view different types of contents. If such an image display device is used, a plurality of users may individually select and view desired contents by using one image display device. Contents displayable in an image display device may include, for example, a broadcast receiving screen, various types of program execution screens, and/or other types of displayable contents. The users input content change commands to view their contents in order to view new contents.
However, if a brightness adjusting method such as an existing adaptive brightness limiter (ABL) is applied to each of image frames of a plurality of contents, it is difficult to realize brightness and an image quality corresponding to each of the contents. If a display panel including a self-emission display device such as an organic light-emitting display device is used, this problem causes a switching mode power supply (SMPS) load problem, thereby deteriorating a performance of the self-emission display device.